B
ulletin F-43
DWYER INSTRUMENTS, INC.
Phone: 219/879-8000 www.dwyer-inst.com
Specifications - Installation and Operating Instructions
Series RM Rate-Master
®
Flowmeters
F
A
B
C
J
B
ACK WIDTH
K
D
E
G
H
I
FULL OPEN
L
The Series RM Rate-Master
®
Flowmeters are furnished in three models (see Fig.
2), each available in a broad array of flow ranges with direct reading scales for air,
gas or water. Installation, operation and maintenance are very simple. Only a few
common-sense precautions must be observed to assure long, trouble-free service.
CAUTION: Rate-Master
®
Flowmeters are designed to provide satisfactory long-
term service when used with air, water or other compatible media. Refer to facto-
ry for information on questionable gases or liquids. Avoid solutions of acids, bases
or salts having a pH below 5.0 or above 8.5. Caustic solutions, antifreeze (ethyl-
ene glycol) and aromatic solvents should definitely not be used.
Calibration
Each Rate-Master
®
Flowmeter is calibrated at the factory. If at any time during the
meter’s life, you wish to re-check its calibration, do so only with devices of certified
accuracy. DO NOT attempt to check a Rate-Master
®
Flowmeter with a similar
flowmeter, as seemingly unimportant variations in piping and back pressure may
cause noticeable differences in the indicated reading. If in doubt, return your Rate-
Master
®
Flowmeter to the factory. Before proceeding with installation, check to be
sure you have the Rate-Master
®
flowmeter model and flow range you require.
LOCATION: Temperature, Pressure, Atmosphere and Vibration: Rate-Master
®
Flowmeters are exceptionally tough and strong. They are designed for use at pres-
sures up to 100 psi (6.89 bar) and temperatures up to 130°F (54°C).
DO NOT EXCEED THESE LIMITS! The installation should not be exposed to
strong chlorine atmospheres or solvents such as benzene, acetone, carbon tetra-
chloride, etc. The mounting panel should be free of excessive vibration, as it may
prevent the unit from operating properly.
A
B
C
D
E
F
G
H
I
(OPEN)
J
K
L
Model RMA
4 -9/16 (11.59)
3 (7.62)
1
/8 NPT CONN.
1
-5/8 (4.13)
1
0 - 32 Thds.
3
/8 (.95)
1-1/16 (2.70)
1-3/16 (3.02)
11/16 (1.75)
6
1/64 (2.42)
1
-3/8 (3.49)
3/4 (1.91)
4-13/16 (12.22)
1 (2.54)
M
odel RMB
8
-1/2 (21.59)
6
-7/16 (16.35)
1/4 NPT CONN.
3-15/16 (10.00)
1/4 - 20 Thds.
5
/8 (1.59)
1
-7/8 (4.76)
1
-3/4 (4.45)
1 (2.54)
1-7/16 (3.65)
1-13/16 (4.60)
1
-1/4 (3.18)
8
-3/4 (22.23)
1
-1/2 (3.81)
D
imensions in Inches (Centimeters)
Model RMC
15 -1/8 (38.42)
1
2 -1/4 (31.12)
1
/2 NPT CONN.
8
-3/4 (22.23)
3
/8 - 24 Thds.
1 (2.54)
2-3/4 (6.99)
2-1/2 (6.35)
1
-7/16 (3.65)
1
-31/32 (5.00)
2
-1/2 (6.35)
2 (5.08)
15-3/8 (39.05)
2-1/4 (5.72)
Inlet Piping Run: It is good practice to approach the flowmeter inlet with as few
elbows and restrictions as possible. In every case, the inlet piping should be at
least as large as the connection to the flowmeter; i.e.,1/8˝ Iron Pipe Size for RMA
models 1/4˝ IPS for RMB models,1/2˝ IPS for RMC models. Length of inlet piping
makes little difference for normal pressure-fed flowmeters.
For flowmeters on vacuum air service, the inlet piping should be as short and open
as possible. This will allow operation near atmospheric pressure and thereby
insure the accuracy of the device. (Note: for vacuum air service, the flow control
valve, if any, should be on the discharge side of the flowmeter. Either the TMV unit
or a separate in-line valve may be applied.).
Discharge Piping: As on the inlet, discharge piping should be at least as large as
the flowmeter connection. Also, for pressure-fed flowmeters on air or gas service,
the discharge piping should be as short and open as possible. This will allow oper-
ation of the flow tube at near atmospheric pressure and insure the accuracy of the
device. This is of less importance on water or liquid flowmeters, as the flowing
medium is generally incompressible and moderate back pressure will not affect the
accuracy of the instrument as calibrated.
POSITIONING AND MOUNTING
All Rate-Master
®
Flowmeters must be mounted in a vertical position with inlet con-
nection at the bottom rear and outlet at the top rear.
Bezel or Through-Panel Mounting: Make panel cutout using appropriate dimen-
sions from Fig. 2. Flowmeter must fit into panel freely without forcing or squeezing.
Insert the flowmeter from the front of the panel and install the mounting clamps
from the rear. Insert and tighten the clamp bolts in the locations shown in Fig. 3.
Do not exceed 5 in./lbs. Make connections to inlet and outlet ports using pipe
thread sealant tape to avoid leakage. Avoid excess torque, which may damage the
flowmeter body.
Panel Cutout For Flush Mounting
4
-5/8 (11.75)
7
/8 (2.22)
7/16 (1.11)
1/4 (0.64)
8-9/16 (21.75)
1-5/16 (3.33)
5/8 (1.59)
9/32 (0.71)
15 -3/16 (38.58)
2
-1/16 (5.24)
1
5/16 (2.38)
13/32 (1.03)
H
igh
Wide
Pipe
Bolt
Fig. 1
Fig. 2
P
anel Hole Sizes for Surface Mounting
RMC RMB-SSV RMA-TMV
MOUNTING
BRACKET
SCREW 4
R
EQUIRED
F
ig. 3
Fig. 4
Fig. 5
F
ig. 6
F
ig. 7
F
ig. 5B
Fig. 6B
S
urface Mounting: Drill appropriate holes in panel, using the dimensions shown
i
n Fig. 2. Hold the flowmeter in position in front of the panel and install the clamp
bolts from the rear. (The mounting clamps may be used as washers, if desired, by
installing them backwards or straightening them out.) Pipe up inlet and discharge
following the directions in the previous sections.
S
urface Mounting on Piping Only: An alternate method of surface mounting,
o
mitting the clamp bolts and supporting the flowmeter solely on the connecting pip-
ing, is possible. For this method, extra-long or straight pipe threads should be used
so that nuts may be run onto the pipe and later tightened against the back of the
panel to retain the unit in proper position. Use appropriate hole layout in formation
from Fig. 2, but omit the small holes.
Surface Mounting on Piping Only Without Panel: For a temporary or laboratory
type installation, the panel may be omitted altogether and the flowmeter installed
d
irectly in rigid piping. Its light weight permits this without difficulty.
O
PERATION
To start system, open valve slowly to avoid possible damage. Control valves on BV
and SSV models are turned clockwise to reduce flow, counter-clockwise to
increase flow (valve is designed for flow adjustment only, not intended to be used
as an open/shut-off valve). A nylon insert is provided in the threaded section of the
valve stem to give a firm touch to valve and to prevent change of setting due to
vibration.
The performance of low range units used in air or gas applications may be affect-
ed by static electricity. Excessive static charge may cause the ball float to behave
erratically or provide a false reading. To ensure the proper function of the unit, the
application should be designed to minimize or dispel static electricity.
The standard technique for reading a Variable Area Flowmeter is to locate the high-
est point of greatest diameter on the float, and then align that with the theoretical
center of the scale graduation. In the event that the float is not aligned with a grad,
an extrapolation of the float location must be made by the operator as to its loca-
tion between the two closest grads. The following are some sample floats shown
with reference to the proper location to read the float.
Variable Area Flowmeters used for gases are typically labeled with the prefix “S” or
“N”, which represents “Standard” for English units or “Normal” for metric units. Use
of this prefix designates that the flowmeter is calibrated to operate at a specific set
of conditions, and deviation from those standard conditions will require correction
for the calibration to be valid. In practice, the reading taken from the flowmeter
scale must be corrected back to standard conditions to be used with the scale
units. The correct location to measure the actual pressure and temperature is at the
exit of the flowmeter, except when using the Top Mounted Valve under vacuum
applications, where they should be measured at the flowmeter inlet. The equation
to correct for nonstandard operating conditions is as follows:
Q
2
= Q
1
x P
1
x T
2
P
2
x T
1
Where: Q
1
= Actual or Observed Flowmeter Reading
Q
2
= Standard Flow Corrected for Pressure and Temperature
P
1
=
Actual Pressure (14.7 psia + Gage Pressure)
P
2
=
Standard Pressure (14.7 psia, which is 0 psig)
T
1
= Actual Temperature (460 R + Temp °F)
T
2
= Standard Temperature (530 R, which is 70°F)
Example: A flowmeter with a scale of 10-100 SCFH Air. The float is sitting at the 60
g
rad on the flowmeter scale. Actual Pressure is measured at the exit of the meter
a
s 5 psig. Actual Temperature is measured at the exit of the meter as 85°F.
Q
2
= 60.0 x (14.7 + 5) x 530
14.7 x (460 + 85)
Q
2
= 68.5 SCFH Air
CAUTION: Do not completely unscrew valve stem unless the flowmeter is unpres-
surized and drained of any liquid. Removal while in service will allow gas or liquid
t
o flow out the front of the valve body and could result in serious personal injury.
F
or applications involving high pressure and/or toxic gases or fluids, please con-
t
act factory for details.
MAINTENANCE
The only maintenance normally required is occasional cleaning to assure reliable
operation and good float visibility.
Disassembly: The flowmeter can be disassembled for cleaning simply as follows:
1. Remove valve knob from RMB or RMC -BV or -SSV units by pulling the knob
forward. It is retained by spring pressure on the stem half-shaft so that a gentle pull
will remove it. On RMA-BV or -SSV models, turn the valve knob counter-clockwise
until the threads are disengaged. Then withdraw the stem from the valve by gently
pulling on the knob.
2. Remove the four mounting bracket screws located in the sides of the flowme-
ter. See Fig. 3. Pull the flowmeter body gently forward away from the back plate to
avoid undue strain on the body. Leave the piping connections intact. There is no
need to disturb them. See Fig. 4.
3. Threaded body style flowmeters - Remove the slip cap with a push on a screw-
driver as shown in Fig. 5. Remove the plug ball stop as shown in Fig. 6 using allen
wrench sizes as follows: Model RMA - 1/4˝, Model RMB - 1/2˝ and Model RMC -
3/4˝ Threadless body style flowmeters - Release the plastic retaining clip with a
screw driver (Figure 5B), it will unclip from the valve body (TMV Option) or the plug
ball stop, slide the clip back until the valve body or ball stop can be removed. The
clip will remain in the body for convenience. Using a screwdriver gently lift up on
the plug in the groove as shown in Figure 6B until the o-ring seal is released and
remove the plug. For the TMV option gently pull up on the valve knob to release
the valve body seals and remove the valve.
4. Take out the ball or float by inverting the body and allowing the float to fall into
your hand, as shown in Fig. 7. (Note: It is best to cover the discharge port to avoid
losing the float through that opening.)
Cleaning: The flow tube and flowmeter body can best be cleaned with a little pure
soap and water. Use of a bottle brush or other soft brush will aid the cleaning. Avoid
benzene, acetone, carbon tetrachloride, alkaline detergents, caustic soda, liquid
soaps (which may contain chlorinated solvents), etc. Also, avoid prolonged immer-
sion, which may harm or loosen the scale.
Reassembly: Simply reverse steps 1 through 4 and place the flowmeter back in
service. A little stopcock grease or petroleum jelly on the “O” rings will help main-
tain a good seal as well as facilitate assembly. No other special care is required.
DWYER INSTRUMENTS, INC.
Phone: 219/879-8000 www.dwyer-inst.com
©Copyright 2015 Dwyer Instruments, Inc. Printed in U.S.A. 3/15 FR# 440197-00 Rev. 23
Teflon
®
is a registered Trademark of E.I. DuPont Company
/
